How many of us have chosen to become geophysicists after an undergraduate course in which programming vibroseis correlation was one of the assignments? The first time a student understands the mathematical foundation of vibroseis is often an epiphany. The topic is a microcosm of seismology, requiring knowledge of the Fourier transform, convolution, reflection coefficient series, correlation, amp-litude and phase spectra, all aimed at the final unlikely goal of recovering a band-limited estimate of subsurface reflection coefficients by injecting a long, slowly varying signal into the ground with a truck the size of a bus. But it worked, and we went from explosive sources with only two crude control levers (shot depth and charge size) to a source with a dashboard of fine-tuning control knobs (number of vibes, source array, sweep length, up- or down-sweep, and so on).

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